The present invention relates to lens apparatuses such as zoom lenses, and to image-taking apparatus with the same, such as digital cameras and video cameras.
Conventional image-taking apparatuses, such as digital cameras and video cameras, are known on which an interchangeable rear focus zoom lens can be mounted or a rear focus zoom lens is provided integrally. The rear focus zoom lens (or inner focus zoom lens) includes a magnification-varying lens, and a focus lens disposed at a position closer to an image plane than the magnification-varying lens. The focus lens corrects (or compensates) image plane displacements caused by the movement of the magnification-varying lens, and performs focusing.
The above-described rear focus zoom lens is generally constituted by a front lens unit (or first lens unit), a variator lens unit (or second lens unit) for varying the magnification, an afocal lens unit (or third lens unit), and a focus lens unit (or fourth lens unit) having a compensating function, the lens units being arranged in order from the object side to the image side.
In a lens apparatus with such a rear focus zoom lens, the focus lens unit, the afocal lens unit, a stop unit, and the variator lens unit are assembled in this order on a rear barrel that is a base member on which an image-pickup element, such as a CCD sensor, is mounted. And finally, the front lens unit is assembled on the rear barrel.
FIG. 5 shows an example of such a conventional rear focus zoom lens. In FIG. 5, 61 denotes a first lens unit, 62 a second lens unit, 63 a third lens unit, and 64 a fourth lens unit.
The first lens unit 61, second lens unit 62, third lens unit 63, and fourth lens unit 64 are held by first lens-holding member 65-1, second lens-holding member 65-2, third lens-holding member 623, and fourth lens-holding member 627, respectively.
The second lens unit 62 is moved with the movement of the second lens-holding member 65-2 that is guided by a straight-proceeding key 611 provided on a fixed lens barrel 610. The fourth lens unit 64 is moved with the movement of the fourth lens-holding member 627 that is guided by a straight-proceeding key 625 provided on the fixed lens barrel 610.
The first lens-holding member 65-1 and third lens-holding member 623 are held by the fixed lens barrel 610.
In a zoom lens apparatus disclosed in Japanese Patent Laid-Open Application No. H7-120663, a first lens barrel unit in which the first lens unit and the second lens unit are unitized and a second lens barrel unit in which the third lens unit and the fourth lens unit are unitized are assembled to each other for facilitating the assembly and optical adjustment of the lens apparatus.
However, in the conventional zoom lens apparatus shown in FIG. 5, the straight-proceeding keys guiding straight the lens-holding members that hold the second and fourth lens units are provided on the fixed lens barrel that holds the first and third lens units. Therefore, it is difficult to make an optical adjustment of each lens unit (for example, adjustment of tilting and decentering with respect to the optical axis) separately from the other lens units.
In addition, since the fixed lens barrel holding the first to fourth lens units has a long length in the optical axis direction, mounting the third and fourth lens unit into the fixed lens barrel needs extra efforts, and the maintenance is difficult.
Moreover, in the zoom lens apparatus disclosed in Japanese Patent Laid-Open Application No. H7-120663, since a lens barrel unit is constituted by two lens units, it is difficult to make the optical adjustment of each lens unit separately from the other lens unit.